C NC NO M 2 3 4 5 6 7 IN IN OUT M 1 2 3 4 5 6 7 P M B P M B 1 1A 1A RESTRICTOR 2 3 1 1 2 3 SEQUENCE OF OPERATION -The fan runs continuously to suit the laboratory operations. -Solenoid valve (EP1) passes control air to the fan controls when the fan is running. -Receiver controller (RC1) senses the return air temperature via transmitter (TT1) and receives a set point demand from (SP ADJ 1). RC1 sends its signal to biasing relays (BR1) and (BR2) as well as to cooling valve (V2). The instrument arrangement causes the heating valve (V1) to close first, then the free cooling via damper actuators (D1) and (D2) is maximized and then mechanical cooling is employed via V2 on a call for cooling. -BR1 sends its signal to high selector (HS1) which also receives a signal from regulator (PRV1) to assure the system of at least minimum ventilation while the fan is running. -Receiver controller (RC3) senses the outside air temperature via transmitter (TT3). RC3 passes its signal to receiver controller (RC2) only when free cooling is available, based on the outside air temperature to economize on mechanical cooling. RC2 senses the mixed air temperature via transmitter (TT2). RC2 limits the mixed air to a minimum of 58°F. -Turn down ratio relay (BR3) is set to limit the range of set point demand from the laboratory. -If low limit (LL1) senses a temperature below its set point on any one foot of its element the fan will shut down. If high limit (HL1) senses a temperature above its set point the fan will shut down. Both LL1 and HL1 require resetting after being tripped. 8.77 DRAWING FIVE PRV 5# HS1 BR1 1:2 RATIO SET 8# IN = 3# OUT EP1 BR2 1:2 RATIO 6# IN = 12# OUT B M 1 2 3 B M 1 2 3 B M 1 2 3 RETURN RC1 MIXED AIR RC2 OSA HL RC3 DA 58˚F DA 70˚F RA 70˚F RETURN MIXED AIR OSA TEMP. TEMP TEMP. SUPPLY TEMP. BR3 M S B SP ADJ.1 DIAL MARKED FOR THERMAL VALUES PER MARK LOCATED ON COLUMN IN LAB. RETURN FAN SUPPLY FAN TT3 TT2 TT4 TT1 HL1 NC NO NC OSA EX. 3# - 13# D2 3# - 13# D1 LL1 PP 13# - 16# V2 V1 PUMP NC C NO NO C NC CWR CWS HWS HWR 5# - 12# RETURN AIR RESTRICTOR RESTRICTOR RESTRICTOR RESTRICTOR
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